Capacity and Queue Modeling for On-Ramp–Freeway Junctions

Abstract

With reference to the procedure in the Highway Capacity Manual (HCM) 2000 for estimation of measures of effectiveness, a model is proposed to estimate merge-area capacity and to predict traffic dynamics and queue evolution for on-ramp–freeway junctions. The aims of the study are to analyze the behavior of flows within the merge area and to propose a methodology to dynamically estimate the capacity of both ramp and main line according to inflow patterns and to develop a mesoscopic model of merge facilities that allows the prediction of merge-area traffic outflow according to inflow patterns and to estimate traffic queue dynamics. The most relevant finding of the study is a methodology for estimation of the capacity of the merge area referred separately to both the main line and the ramp. The proposed approach could be considered as a link between the HCM hypotheses and those of gap-acceptance theory; the capacity of the competitive streams within the merge area depends on the opposing traffic volumes. The model gives information about traffic flows and queue dynamics (including total delay and maximum queue length). The first results of the application to a case study are briefly discussed, and some further developments are suggested.